<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .box{
            font-size: 30px;
        }
        .a >span{
            text-transform: capitalize;
        }
        .b >span{
            text-transform: uppercase;
        }
        .c >span{
            text-transform: lowercase;
        }
    </style>
</head>
<body>
    <h2>text-transform: capitalize;</h2>
    <div class="box a">hello world: <span>hello world</span></div>
    
    <hr>
     <h2>text-transform: uppercase;</h2>
    <div class="box b">hello world: <span>hello world</span></div>

    <hr>
    <h2>text-transform: lowercase;</h2> 
    <div class="box c">HELLO WORLD: <span>HELLO WORLD</span></div>    
</body>
</html>